Beirut: Syrian President Bashar Assad made his first appearance since a brazen bomb attack killed three members of his inner circle while government troops launched a wide-ranging assault on Thursday to snuff out rebels throughout the capital Damascus.

Anti-regime activists said government troops used mortars, tanks and helicopter gunships against rebels throughout Damascus and its suburbs. But the military's failure to swiftly vanquish lightly armed rebel forces and the deadly bombing of a high-level security meeting a day earlier made Assad's hold on power look increasingly tenuous.

Amateur video showed rebels taking over the Bab al-Hawa border crossing with Turkey, where they stomped on portraits of Assad and his father and predecessor, Hafez Assad.

The whereabouts of Assad, his wife and their three young children have been a mystery since the attack that killed his brother-in-law and defense minister. Assad does not appear in public frequently, but his absence was notable following such a serious blow to his inner circle.

A brief state TV report showed Assad dressed in a suit and tie and swearing-in his new defense minister. It appeared aimed at sending the message that Assad is alive and well. The station said that he wished the new defense minister good luck, but did not say where the swearing-in took place.

Thousands of Syrians streamed across the Syrian border into Lebanon, fleeing as fighting in the capital entered its fifth straight day, witnesses said. Residents near the Masnaa crossing point -- about 40 kilometres from Damascus – said hundreds of private cars as well as taxis and buses were ferrying people across.

Yesterday's rebel bomb attack struck the harshest blow yet to Assad's regime. The White House said it showed Assad was "losing control" of Syria.

Syrian TV confirmed the deaths of Defence Minister Dawoud Rajha, 65, a former army general and the most senior government official to be killed in the rebels' battle to oust Assad; Gen Assef Shawkat, 62, the deputy defence minister who is married to Assad's elder sister, Bushra, and is one of the most feared figures in the inner circle; and Hassan Turkmani, 77, a former defence minister who died of his wounds in the hospital.

Also wounded were Interior Minister Mohammed Shaar and Maj Gen Hisham Ikhtiar, who heads the National Security Department. State TV said both were in stable condition.

Rebels claimed responsibility, saying they targeted theroom where the top government security officials in charge of crushing the revolt were meeting.